const str = 'hello world'
const num = 123
const flag = true
const u = undefined
const n = null
const s = Symbol(1)
const big = 123n

const arr = [1, 3, 2, 's']

const obj = {
  name: '牛哥',
  age: 18,
  like: ['running', 'rap'],
  info: {
    city: '南昌'
  }
}

class Person{
  
}